Our basic customer service philosophy is simple:
Greet - make sure to greet the user as they approach you - you should see them before they reach the desk, and be ready to say hello and offer help
Listen - listen carefully to what the user asks, and make sure to follow up to confirm you understand what they are looking for, or what their problem is.
Answer - answer their question! Get them their book! Basically, provide what they are looking for.
Offer - don't leave the user with just the answer to their question, make an offer! Whether this is "is there anything else we can help you with?" or "let me get your contact info - I'll pass your problem along to my supervisor and they will check in with you," make sure that the user leaves, if not happy, at least assured that we did everything we could to help.